adrenergic f's nerve fibers of the sympathetic nervous system that liberate norepinephrine (and possibly small amounts of epinephrine) at a synapse when a nerve impulse passes.

alpha f's motor and proprioceptive fibers of the A type having conduction velocities of 70 to 120 meters per second and ranging from 13 to 22 micrometers in diameter.

arcuate f's any of the bow-shaped fibers in the brain, such as those connecting adjacent gyri in the cerebral cortex, or the external or internal arcuate fibers of the medulla oblongata.

association f's nerve fibers that interconnect portions of the cerebral cortex within a hemisphere. Short association fibers interconnect neighboring gyri; long fibers interconnect more widely separated gyri and are arranged into bundles or fasciculi.

B f's myelinated preganglionic autonomic axons having a fiber diameter less than 3 μm and a conduction velocity of 3 to 15 meters per second.

beta f's touch and temperature fibers of the A type having conduction velocities of 30 to 70 meters per second and ranging from 8 to 13 micrometers in diameter.

C f's postganglionic unmyelinated fibers of the autonomic nervous system; also, the unmyelinated fibers at the dorsal roots and at free nerve endings having a diameter of 0.3 to 1.3 μm and a conduction velocity of 0.6 to 2.3 meters per second.

cholinergic f's nerve fibers such as the parasympathetic fibers that liberate acetylcholine at a synapse when a nerve impulse passes.

collagen f's (collagenous f's) the soft, flexible, white fibers that are the most characteristic constituent of all types of connective tissue, consisting of the protein collagen, and composed of bundles of fibrils that are in turn made up of smaller units (microfibrils) that show a characteristic crossbanding with a major periodicity of 65 nm.

Corti's f's pillar cells.

crude fiber the fiber that remains after food is digested with alkali and acid, which destroys all soluble and some insoluble fiber. It is mainly lignin and cellulose.

dietary fiber that portion of ingested foodstuffs that cannot be broken down by intestinal enzymes and juices and, therefore, passes through the small intestine and colon undigested. It is composed of cellulose (which is the “skeleton” of plants), hemicellulose, gums, lignin, pectin, and other carbohydrates indigestible by humans. Dietary fiber is not to be confused with crude fiber, which is the term used in the USDA Handbook and other tables listing the composition of foods. Crude fiber is mainly lignin and cellulose and is the residue remaining after a food has been subjected to a standardized treatment with dilute acid and alkali. Crude fiber measurements usually underestimate actual total dietary fiber by at least 50 per cent.

Vegetables, cereals, and fruits are the main sources of dietary fiber. Although bran is advertised as an excellent source of fiber, it is not unique nor is it as nutritious as fruits and vegetables and some other whole unprocessed cereals. The typical diet in Western countries contains 10 to 30 grams of dietary fiber.

The primary effects of dietary fiber are to increase the bulk of the stool and make it softer by taking up water as it passes through the colon, and to absorb organic wastes and toxins and carry them out of the intestinal tract. The increase in stool bulk hastens the passage of feces and may reduce the length of time the intestinal wall is exposed to toxic substances.

Benefits of a High Fiber Diet. Dietary fiber is helpful in the treatment and prevention of uncomplicated constipation. Unlike strong laxatives, it presents no problems when taken on a long-term basis. Metamucil, a medicinal fecal softener, is made from seed husks and is often prescribed for persons having problems with normal bowel activity. Hemorrhoids are aggravated by straining on defecation, and so there is some basis for recommending a high fiber diet for persons who have this condition.

The symptoms of diverticular disease, which is an outpouching of the wall of the colon with subsequent inflammation, are relieved by a high fiber diet. There is evidence to support the theory that the more rapid passage of softer stools through the colon decreases the pressure exerted against its walls and thereby prevents formation of diverticula.

The symptoms of irritable bowel syndrome often can be mitigated by fiber. The bulk of fiber keeps the colon mildly distended, thus preventing the development of pockets of high pressure that cause spasm. However, inflammatory bowel disease in which there is a narrowing of the bowel, as in some cases of crohn's disease, can be worsened by more roughage in the intestinal tract.

Fiber does have the capacity to unite with intestinal bile salts and dietary cholesterol, preventing their absorption from the gut and hastening their elimination via the intestinal tract. Because of these properties, fiber has been advocated as a preventive measure against the formation of gallstones and the production of atherosclerotic plaques in the blood vessels.

In diabetes mellitus, fiber, when eaten with other foods, somewhat reduces the rise in blood glucose that occurs after eating. Fiber slows the rate of carbohydrate breakdown and absorption from the intestinal tract. The American Cancer Society suggests a diet rich in fiber as a way to lower the incidence of certain kinds of cancer, particularly colorectal cancer.

Some people may have difficulties with a high fiber diet. It can produce abdominal pain, bloating, flatus, and diarrhea. These side effects can be controlled if the fiber is introduced to the diet in small amounts and with an increase in fluid intake. Excessive amounts of fiber can also impair absorption of essential minerals.

gamma f's fibers that conduct touch and pressure impulses and innervate the intrafusal fibers of the muscle spindle; they conduct at velocities of 15 to 40 meters per second and range from 3 to 7 μm in diameter.

insoluble fiber that not soluble in water, composed mainly of lignin, cellulose, and hemicelluloses and primarily found in the bran layers of cereal grains. Its actions include increasing fecal bulk and decreasing free radicals in the gastrointestinal tract.

light f's muscle fibers poor in sarcoplasm and more transparent than dark fibers.

Mahaim f's short direct connections between the lower atrioventricular node or bundle of His and the ventricular septum, resulting in preexcitation of the ventricular septum and a delta wave. Only right sided connections have been described.

muscle fiber any of the cells of skeletal or cardiac muscle tissue. Skeletal muscle fibers are cylindrical multinucleate cells containing contracting myofibrils, across which run transverse striations. Cardiac muscle fibers have one or sometimes two nuclei, contain myofibrils, and are separated from one another by an intercalated disk; although striated, cardiac muscle fibers branch to form an interlacing network.

muscle f's, fast twitch paler-colored muscle fibers of larger diameter than slow twitch fibers, and having less sarcoplasm and more prominent cross-striping; used for forceful and rapid contractions over short periods of time.

muscle f's, slow twitch small dark muscle fibers rich in mitochondria, myoglobin, and sarcoplasm and with only faint cross-striping; designed for slow but repetitive contractions over long periods of time.

projection f's bundles of axons that connect the cerebral cortex with the subcortical centers, brain stem, and spinal cord.

Purkinje f's modified cardiac fibers in the subendocardial tissue that constitute the terminal ramifications of the conducting system of the heart. The term is sometimes used loosely to denote the entire system of conducting fibers.

radicular f's fibers in the roots of the spinal nerves.

ragged red f's muscle fibers characterized by large collections of structurally abnormal mitochondria below the sarcolemmal surface and within the fiber itself that stain red; seen in mitochondrial myopathy and certain other myopathic disorders.

reticular f's immature connective tissue fibers, staining with silver, forming the reticular framework of lymphoid and myeloid tissue, and occurring in interstitial tissue of glandular organs, the papillary layer of the skin, and elsewhere.

Sharpey's f's

1. collagenous fibers that pass from the periosteum and are embedded in the outer circumferential and interstitial lamellae of bone.

2. terminal portions of principal fibers that insert into the cementum of a tooth.

soluble fiber that with an affinity for water, either dissolving or swelling to form a gel; it includes gums, pectins, mucilages, and some hemicelluloses, and is primarily found in fruits, vegetables, oats, barley, legumes, and seaweed. It acts to decrease the rate of stomach emptying and increase transit time through the intestine, and also binds bile acids, increasing their excretion. Soluble fiber appears to specifically lower levels of low-density lipoproteincholesterol.

fiber

A fibers myelinated afferent or efferent fibers of the somatic nervous system having a diameter of 1 to 22 μm and a conduction velocity of 5 to 120 meters per second; they include the alpha, beta, delta, and gamma fibers.

beta fibers motor and proprioceptive fibers of the A type, having conduction velocities of 30 to 70 meters per second and ranging from 8 to 13 μm in diameter.

C fibers unmyelinated postganglionic fibers of the autonomic nervous system, also the unmyelinated fibers at the dorsal roots and at free nerve endings, having a conduction velocity of 0.6 to 2.3 meters per second and a diameter of 0.3 to 1.3 μm.

collagen fibers , collagenous fibers the soft, flexible, white fibers which are the most characteristic constituent of all types of connective tissue, consisting of the protein collagen, and composed of bundles of fibrils that are in turn made up of smaller units (microfibrils), which show a characteristic crossbanding with a major periodicity of 65 nm.

commissural fiber one of the nerve fibers which pass between the cortex of opposite hemispheres of the brain, or between two sides of the brain stem or spinal cord.

dietary fiber that part of whole grains, vegetables, fruits, and nuts that resists digestion in the gastrointestinal tract; it consists of carbohydrate (cellulose, etc.) and lignin.

muscle fiber any of the cells of skeletal or cardiac muscle tissue. Skeletal muscle fibers are cylindrical multinucleate cells containing contracting myofibrils, across which run transverse striations. Cardiac muscle fibers have one or sometimes two nuclei, contain myofibrils, and are separated from one another by an intercalated disk; although striated, cardiac muscle fibers branch to form an interlacing network.

myelinated fibers grayish white nerve fibers whose axons are encased in a myelin sheath, which may in turn be enclosed by a neurilemma.

nerve fiber a slender process of a neuron, especially the prolonged axon which conducts nerve impulses away from the cell; classified as either afferent or efferent according to the direction the impulses flow, and either myelinated or unmyelinated according to whether there is or is not a myelin sheath.

projection fiber , projection nerve fibers one of the nerve fibers that connect the cerebral cortex with the subcortical centers, the brain stem, and the spinal cord.

Purkinje fibers modified cardiac muscle fibers composed of Purkinje cells, occurring as an interlaced network in the subendothelial tissue and constituting the terminal ramifications of the cardiac conducting system.

radicular fibers fibers in the roots of the spinal nerves.

reticular fibers immature connective tissue fibers staining with silver, forming the reticular framework of lymphoid and myeloid tissue, and occurring in interstitial tissue of glandular organs, the papillary layer of the dermis, and elsewhere.

1. collagenous fibers that pass from the periosteum and are embedded in the outer circumferential and interstitial lamellae of bone.

2. terminal portions of principal fibers that insert into the cementum of a tooth.

soluble fiber that with an affinity for water, either dissolving or swelling to form a gel; it includes gums, pectins, mucilages, and some hemicelluloses, and is primarily found in fruits, vegetables, oats, barley, legumes, and seaweed.

fiber

1. Botany One of the elongated, thick-walled cells that give strength and support to plant tissue.

2. Anatomy

a. Any of the filaments constituting the extracellular matrix of connective tissue.

b. Any of various elongated cells or threadlike structures, especially a muscle fiber or a nerve fiber.

3. Coarse, indigestible plant matter, consisting primarily of polysaccharides such as cellulose, that when eaten stimulates intestinal peristalsis. Also called bulk, roughage.

fi′bered adj.

fiber

[fī′bər]

1 a long, filmlike, threadlike, acellular structure found in plant and animal tissues. Plant fibers usually consist of structural carbohydrates such as cellulose in cell walls. Composed of repeating glucose units in long, single strands, cellulose cannot be digested by enzymes in the human intestine. Other plant fiber components include hemicellulose and pectin. Animal fibers are composed mainly of the protein collagen, which forms elastic threads of loose connective tissue in skin and other organs. See also dietary fiber.

2 a skeletal muscle cell.

3 the axon of a nerve cell.

fiber

Nutrition Bulk, roughage The indigestible part of fruits and vegetables, which may have a cancer-preventive effect. See Bran, Crude fiber, Dietary fiber, Oat bran, Soluble fiber.

fiber,

n one of three types of fiber; soluble fibers are pectin, gum mucilage, and glucomannan and are found in pears, apples, vegetables, and wheat bran.

fiber, sweeping cross,

n massage technique that closely resembles gliding or effleurage. Distinguished by the addition of light cross-fiber strokes (direction of movement is perpendicular to the pattern of muscle fibers) that penetrate deeper tissues. See also effleurage.

fi·ber

2. Nutrients in the diet that are not digested by gastrointestinal enzymes. Synonym(s): fibre.

[L. fibra]

fiber(s),

n an elongated, threadlike structure of organic tissue.

fibers, A-alpha nerve,

n.pl the large-diameter nerve fibers that connect into the substantia gelatinosa of the dorsal horns of the spinal cord before synapsing with the central transmission of the dorsal horn. A-alpha fibers are associated with the “gate-control” theory of pain.

fibers, A-beta nerve,

n.pl the large-diameter nerve fibers that are mechanoreceptors for pressure occurring in both the pulp and periodontal ligament, necessary to operate the gate mechanism.

fibers, A-delta nerve,

n.pl the small-diameter nerve fibers that are mechanoreceptors for pain occurring in both the pulp and the periodontal ligament, necessary to operate the gate mechanism.

fibers, adrenergic

(ad´rəner´jik), n.pl the nerve fibers, including most of the postganglionic sympathetic fibers, that transmit their impulses across synapses or neuroeffector junctions through the local release of the neurohormone, more recently identified as norepinephrine and formerly designated sympathin.

fibers, alveolar,

n.pl the collagen fibers of the periodontal ligament that extend from the alveolar bone to the intermediate plexus, where their terminations are interspersed with the terminations of the cemental group of fibers.

fibers, alveolar crest,

n.pl the collagen fibers of the periodontal ligament that extend from the cervical area of the tooth to the alveolar crest.

fibers, alveolgingival,

n.pl the collagen fibers of the periodontal ligament that extend from the alveolar crest into the gingiva.

fibers, apical,

n.pl the collagen fibers of the periodontal ligament radiating apically from tooth to bone.

fibers, association,

n.pl the extensions of nerve cells that are neither efferent nor afferent neurons but furnish a pathway of connection between them.

fibers, bundle,

n.pl the gathering together of collagen fibers in a group, particularly the collagen fiber bundles of the periodontal ligament.

fibers, C nerve,

n.pl the small-diameter nerve fibers that are mechanoreceptors for pain occurring in both the pulp and the periodontal ligament, necessary to operate the gate mechanism.

fibers, cemental,

n.pl the collagen fibers of the periodontal ligament extending from the cementum to the zone of the intermediate plexus, where their terminations are interspersed with the terminations of the alveolar group of periodontal fibers.

fibers, circular,

n.pl the collagen fibers in the free gingiva that encircle the tooth in a ringlike fashion.

fibers, collagen,

n.pl white fibers composed of collagen. The most conspicuous part of connective tissue, including the gingivae and periodontal ligament. Some fibers are distributed haphazardly throughout the connective tissue ground substance, and others are arranged in coarse bundles that exhibit a distinct orientation. Characterized by its hydroxyproline and hydroxylysine content.

fiber, crestal,

n a group of collagen fibers of the periodontal ligament extending from the cervical area of the tooth to the alveolar crest.

fibers, dentogingival,

n.pl the fan-shaped fibers of the periodontal ligament that emerge from the supraalveolar connective tissue; composed of circular, dentogingival, dentoperiosteal, and transseptal (interdental) fiber groups.

fibers, dentoperiosteal,

n the part of the fibers of the periodontal ligament that emerge from the supraalveolar part of the cementum of the tooth and pass outward beyond the alveolar crest in an apical direction into the mucoperiosteum of the attached gingiva.

fibers, gingival,

n the group of fibers of the periodontal ligament that belong to the gingival and supraalveolar connective tissue; composed of circular, dentogingival, dentoperiosteal, and transseptal fiber (interdental) groups.

fibers, horizontal,

n.pl the collagen fibers of the periodontal ligament that extend horizontally from the cementum to the alveolar bone.

fibers, interradicular,

n.pl the collagen fibers of the periodontal ligament noted in multirooted teeth that extend from the cementum to the bone between the roots.

fiber, myelinated nerve

n a nerve fiber inside or outside the brain that is covered with an insulating medullary sheath along which are located nodes of Ranvier that facilitate as relay points the speed of nerve impulses over that of an equivalent nonmedullated fiber.

fibers, nerve,

n.pl See fiber, myelinated nerve, and fiber, nonmedullated nerve.

fibers, nonmedullated nerve

(non´med´əlā´təd), n a nerve fiber not covered by an insulating medullary sheath that is thus exposed to other tissue fluids and their respective electric potentials. In nonmedullated fibers, the impulse is relayed from point to contiguous point. Most of the nonmedullated fibers are within the substance of the central nervous system, and the distances between the cells are short.

Gingival fibers.

Tissues and fibers of the gingiva and attachment apparatus.

fibers, oblique,

n the group of collagen fibers in bundle arrangement in the periodontal ligament that are obliquely situated, with insertions in the cementum, and that extend more occlusally in the alveolus.

n.pl the numerous bundles of collagen fibers arranged in groups that function as the mode of attachment of the tooth to the alveolus and form the periodontal ligament.

fibers, Sharpey's,

n.pr the collagen fibers of the periodontal ligament that become incorporated into the cementum or alveolar bone.

fibers, transseptal,

n.pl a part of the collagen fibers of the periodontal ligament that extends from the supraalveolar cementum of one tooth horizontally through the interdental attached gingiva above the septum of the alveolar bone to the cementum of the adjacent tooth. Also called interdental fibers.

Patient discussion about fiber

Q. Does intake of diet rich in fiber will be beneficial for weight reduction? I feel obesity is a hindrance to a happy life and though many weight reduction and slimming techniques are currently available, how can one choose the correct technique. Does intake of diet rich in fiber will be beneficial for weight reduction?

A. Yes, researches indicate that the normal weight adults tend to eat more fiber and fruit than people who are overweight or obese. The difference found was that the normal-weight adults consume about 33 % more dietary fiber and 43 % more complex carbohydrates each day than people who are obese. Thus it is shown that consumption of a balanced diet that includes an adequate amount of fiber from plant foods will surely benefit your health and weight. You must have fiber rich foods if you are obese.

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